Following its return from the far north of Svalbard, where it had been looking at the incredible ocean life, the Esperanza spent the last few days in Ny-Ålesund. The small Arctic research base looks a lot different since our last visit; a lot of the snow has melted, and the tundra has taken on what appears to us to be a rather intense shade of green – bear in mind, we haven’t seen much green at all for a while, so it’s all relative. The barnacle geese are marching about with furry goslings in tow, and the Arctic fox vixen that has a den beneath the Dutch research station can be seen with her giddy collection of fuzzy grey cubs in tow.

The local human traffic has increased too; we only saw a couple of other vessels visiting the last time, now several cruise ships per day stop in Ny-Ålesund, disgorging hundreds of tourists ashore for a couple of hours at a time.

We left Ny-Ålesund on June 6th, after having help set up the biggest experiment ever to investigate ocean acidification leaving our friends from IFM-GEOMAR to spend the next few weeks investigating future scenarios of what carbon dioxide pollution means for our oceans. The nine big ‘mesocosms’ – 17m high ‘test tubes’, transported from Germany on the Esperanza’s helideck, have spent those weeks anchored just off shore from Ny-Ålesund, each one representing predicted levels of CO2 in the future.

Sometimes referred to as the “the other carbon problem”, ocean acidification is caused by the absorption of carbon dioxide by the ocean. CO2 emissions have been rising since the beginning the industrial era, around one quarter to one third of which get absorbed by the oceans, and the rate of this absorption has increased. Once in the water, it dissolves into a weak, carbonic acid. This in turn is tipping the balance of sea water from its more natural alkaline state towards acidity, a process we call ocean acidification.

This is not a good thing. Even a small shift in the pH of seawater is enough to cause drastic changes in the marine ecosystem and upset the entire food web. One of these changes is a decrease in available carbonate ions – one of the most important build blocks for shell and skeleton-building animals that include corals, shellfish and plankton.

And that’s what Ulf, Sebastian, Jan, and all our friends from IFM-GEOMAR have been investigating. By looking at the changes that occur with the plankton in each mesocosm (which means medium-sized world, by the way), they’ve been collecting data about how our oceans may look in the future, unless we make some serious cuts to our global CO2 emissions.

The five-week experiment was a success; not only do they now have the most comprehensive data set ever on the impacts of ocean acidification in Arctic waters, they’ve observed that ocean acidification in these waters has a definite impact on the base of the food web, which is something that could have implications for the entire ecosystem. They’ll be back in Kiel, Germany, for the next few months, working on this data.

Since before the weekend, it was “all go” in Ny-Ålesund. Working with the scientists and the small ship from UNIS (University of Svalbard) Viking Explorer, the Esperanza’s crew retrieved the huge mesocosms from the fjord.

It’s been heavy and painstaking work, something of a learning process– but it all went really smoothly.

In ‘downtown’ Ny-Ålesund, the Esperanza’s crew were invited an open-air (remember it doesn’t get dark here this time of year) screening of the World Cup Final, in what was probably the most northerly screening of the game. After a month at sea, none of the footie fans on the Esperanza managed to see anything until the Germany-Spain game last week.

On Friday evening, while tonnes of scientific equipment were being loaded onto the Esperanza from the quay, a shout went up - a beluga, one of the beautiful, mysterious white whales, was beside the ship. Unfussed by the all the people watching, it swam slowly into the harbour, and right under our feet, before swimming back off into Kongsfjord.

Uptown, near the dogyard there’s hordes of Arctic terns, eager to protect against any potential approaches to their nearby nests. They screech and swoop at pedestrians; as they go for the highest point, it’s wise to carry something above you, on an outstretched arm, if you go walkabout in this little town at the top of the world.

The Arctic Under Pressure 2010 expedition has now come to an end –the Esperanza has departed Ny-Ålesund and will soon head back to Europe, with the mesocosms on board, but the work to protect the Arctic from industrial development, and to convince governments to commit to CO2 emissions will continue.